fill

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries the full burden, and it does disclose one genuine behavioral trait: it refuses password and credential selectors. That is useful, but it omits other behaviors an agent needs, such as whether existing content is cleared, waiting/visibility handling, and what happens on a failed selector.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences with no filler, and the core action is front-loaded ahead of the security caveat. It is slightly under-specified rather than padded, so the size is appropriate but leaves gaps.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so return values need not be explained, and the security caveat is covered. However, for a browser-automation write tool with zero annotations and zero schema coverage, missing selector-format and failure/replace behavior leaves the agent with notable blind spots.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 0% and neither parameter has a description. The description implies 'selector' identifies the input field and that a value is supplied, but it adds no syntax detail (CSS vs XPath), no clarification that value is the text to type, and no compensation for the documentation gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Fill') and resource ('an input field'), so the agent knows this writes text into a DOM element. It does not explicitly differentiate itself from siblings like click, evaluate_js, or open_site, but the resource is unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no guidance on when to use fill versus alternatives such as evaluate_js or click, nor any prerequisites (e.g., element must exist/be visible). The only constraint given is the negative one about password selectors, which is a safety rule rather than usage routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.